1. On March 11, 1848, the United States and Great Britain signed the Treaty of Guadalupe Hidalgo, which ended the Mexican-American War and established the border between Texas and Mexico. This treaty indirectly affected Montana, as the U.S. expansion into the West led to the formation of the Montana Territory in 1864.

2. March 11, 1872, marks the establishment of Yellowstone National Park, the world's first national park. Located in Montana, Wyoming, and Idaho, Yellowstone is celebrated for its geothermal features, including Old Faithful geyser and the Grand Prismatic Spring.

3. In 1941, the Anaconda Copper Mining Company shut down its massive smelter in Anaconda, Montana, in response to concerns over environmental pollution. The closure had major economic repercussions for Anaconda and the surrounding area. Today, the Anaconda smelter stack remains a prominent landmark and symbol of the region’s mining heritage.

4. On March 11, 1996, a massive blizzard swept through Montana, causing widespread power outages, travel disruptions, and property damage. The storm, which packed winds of up to 80 miles per hour, was responsible for at least two deaths in the state.

5. March 11, 2012, saw the official opening of the Western Montana Trailhead of the Ice Age National Scenic Trail. This 10-mile section of the trail winds through the picturesque landscapes of the Rocky Mountains, offering hikers stunning views of rivers, forests, and peaks. The Ice Age Trail stretches for over 1,200 miles across Wisconsin, Minnesota, and Michigan, showcasing the geological legacy of continental glaciation.